Crude oil is conventionally processed by distillation followed by various cracking, solvent refining and hydroconversion processes to produce a desired slate of fuels, lubricating oil products, chemicals, chemical feedstocks and the like. An example conventional process includes distillation of a crude oil in an atmospheric distillation column to form a gas oil, naphtha, a gaseous product, and a atmospheric residuum. Generally, the atmospheric residuum is further fractionated in a vacuum distillation column to produce a vacuum gas oil and a vacuum residuum. The vacuum gas oil is usually cracked to more valuable light transportation fuel products by fluid catalytic cracking or hydrocracking. The vacuum residuum may be further treated to recover a higher amount of useful products. Such upgrading methods may include one or more of, for example, residuum hydrotreating, residuum fluid catalytic cracking, coking, and solvent deasphalting. Streams recovered from crude distillation at the boiling point of fuels have characteristically been used directly as fuels.
U.S. Pat. No. 4,885,080 teaches preparing a synthetic crude oil by fractionating a heavy crude oil, hydrodesulfurizing the distillate cut, hydrodemetallizing the residuum and combining the hydrotreated cuts with a third liquid fraction to form the synthetic crude oil. U.S. Pat. No. 3,830,731 teaches distilling a heavy hydrocarbon feedstock into a vacuum gas oil and a vacuum residuum fraction, and hydrodesulfurizing each fraction. However, increasingly tighter regulations on contaminant in fuels, particularly sulfur and aromatics, have forced many refiners to hydrorefine most and often all, of the fuel products. To meet the more stringent requirements for low sulfur diesel, refiners have added naphtha hydrotreaters for removing sulfur and nitrogen compounds from at least some of the refinery streams which go to make up the gasoline pool. In response to the more stringent requirements for clean diesel fuels, refiners have added diesel hydrotreaters for making the low sulfur, low aromatics diesel which are now preferred, and often required. More refiners are building hydrocrackers due to their ability to produce high quality low sulfur fuels. The light gaseous products processed in a refinery are generally treated to remove H2S and others sulfur containing components prior to use of the gaseous products for energy, as petrochemical feedstocks, as reforming feedstocks for making synthesis gas, or as building blocks for turning the gaseous products into higher molecular weight products.
Thus, in response to these tightening regulations, refiners have constructed separate hydroprocessing units to upgrade each of the fuel streams produced in the refinery. The net effect is a large number of similar processing units, each handling a separate stream, requiring additional tankage and operators. Specific streams are alternatively heated for reaction or fractionation, and then cooled for separation and storage. Multiple reaction systems requires multiple hydrogen supply, pressurization and distribution systems. It is desirable to have a process for hydroprocessing the entire crude oil into useful low aromatic, low sulfur products while significantly reducing the number of refinery processing steps and processing equipment required to convert the crude to useful products. Such a process is the subject of the present invention.
In U.S. Pat. No. 5,009,768, a complete crude or the atmospheric and vacuum residues thereof mixed with vacuum gas oils is demetallized and the demetallized product hydrotreated for hydrodenitrogenation and hydroconversion. In U.S. Pat. No. 5,382,349, a heavy hydrocarbon oil is hydrotreated, the hydrotreated oil distilled and a vacuum residue thermally hydrocracked in a slurry bed. U.S. Pat. No. 5,851,381 provides a method of refining crude oil by distillation and desulfurization. In the method, a naphtha fraction is separated from crude oil by distillation, with the remaining residual fraction after the naphtha fraction has been removed from the crude oil being hydrodesulfurized and the hydrodesulfurized fraction separated into further fractions, first in a high pressure separator and then by atmospheric distillation. A residue is further upgraded in a residue fluid catalytic cracking process.